U.S. Pat. No. 3,148,061 describes a method for polymerizing 4-vinyl pyridine monomers using a water-insoluble initiator, i.e, benzoyl peroxide.
U.S. Pat. No. 3,208,964 describes a process for polymerizing 2- or 4-vinyl pyridine monomers in the presence of a polyvinyl alcohol and a water-insoluble initiator, such as, for example, benzoyl peroxide.
U.S. Pat. No. 3,507,856 describes a process for polymerizing vinyl pyridine monomers in the presence of a polyvinyl alcohol and a slightly water-soluble initiator, such as, for example, acetyl peroxide or 2,2'-azobis(methylpropiontrile).
As is generally known in the art, the vinyl pyridine monomers and the initiator are kept separate prior to the polymerization reaction to avoid premature interactions, especially in large-scale production. However, given the limited water solubility of the vinyl pyridine monomer and the initiators as described in the above-mentioned patents, there exists a possibility that, in aqueous polymerization processes, nonuniform reaction initiation, and progression therefrom, may occur, leading, in part, to the presence of appreciable residual vinyl pyridine monomer.
Therefore, it was postulated herein that the use of a water-soluble initiator would facilitate uniform initiation, and thus, result in less, if any, residual 4-vinyl pyridine monomer. It was also thought that use of relatively low amounts of the 4-vinyl pyridine monomer would enable the majority of the 4-vinyl pyridine monomer to be solubilized in water and, thus, would encourage its timely interaction with the water-soluble initiator in such aqueous polymerization processes, and result in a more homogeneous, i.e., weight average molecular weight and particle size, poly-4-vinylpyridine.
It has now been unexpectedly discovered that a process for polymerizing 4-vinyl pyridine monomer in the presence of polyvinyl alcohol which utilizes a water-soluble initiator results in a homogeneous dispersion of poly-4-vinylpyridine, as well as, less if any residual 4-vinyl pyridine monomer.
Therefore, while the aforementioned methods for polymerizing vinyl pyridine monomers are generally suitable for the applications described respectively therein, nonetheless, investigations continue to be pursued to develop novel and improved ways to polymerize vinyl pyridine monomers to provide further advantages.
It is therefore an object of the present invention to provide a novel process for the polymerization of 4-vinyl pyridine monomers.
It is another object of the present invention to provide a novel process for the polymerization of 4-vinyl pyridine monomers in the presence of a polyvinyl alcohol and a water-soluble initiator.
It is another object of the present invention to provide a novel process for the polymerization of 4-vinyl pyridine monomer which results in a homogeneous dispersion of poly-4-vinylpyridine polymer.
It is yet another object of the present invention to provide a novel process for the polymerization of 4-vinyl pyridine monomer which results in no appreciable residual 4-vinyl pyridine monomer.
It is a further object of the present invention to provide a coating fluid prepared by the novel polymerization process.
It is yet a further object of the present invention to provide a coating fluid prepared by the novel polymerization process to coat an ink-receiving layer of an ink jet recording sheet or an image-receiving layer of an image-recording material.
It is a yet another object of the present invention to provide a novel process for polymerizing 4-vinyl pyridine monomers which, when scaled-up for the preparation of larger volumes of coating solutions, allows for better control of the initiation of the polymerization process and prevents any appreciable accumulation of residual 4-vinyl pyridine monomer.